US 20070112405 A1
A catheter used to deliver a medical electrical lead to a right atrium of a heart in close proximity to a His bundle. The catheter is adapted such that the distal tip confronts the His bundle generally perpendicularly. The catheter includes a proximal portion and a generally hook-shaped distal portion. The distal portion may include curves that direct the distal tip at an angle of over 180 degrees from the direction of the proximal portion.
1. A catheter for implanting an electrical lead to a right atrium of a heart in close proximity to a His bundle, the catheter comprising:
a proximal portion; and
a generally hook-shaped distal portion being generally planar, extending distally from the proximal portion, and terminating in a distal tip, the distal portion having a first and second segments, the second segment extending distally of the first segment, the second segment extending through an arc of approximately 100 to 160 degrees to orient the distal tip generally perpendicular to a His bundle when the catheter is implanted, the first segment being formed of a resilient material and having a curvature that springs the second portion toward the His bundle when the catheter is implanted.
2. The catheter of
3. The catheter of
4. The catheter of
5. The catheter of
6. The catheter of
7. The catheter of
8. The catheter of
9. The catheter of
10. The catheter of
11. The catheter of
12. A catheter and lead system for implantation into a right atrium of a heart in close proximity to a His bundle, the catheter and lead system comprising:
a catheter having a proximal portion and a generally hook-shaped distal portion, the distal portion extending distally from the proximal portion and terminating in a distal tip, the distal portion extending over a length greater than 138 millimeters and extending through an arc of at least 180 degrees, the distal portion having a first segment formed with a first radius of curvature and a second segment formed with a second radius of curvature, the second segment being distal of the first segment and curving in the same direction as the first segment, and the first radius of curvature being greater than the second radius of curvature, the second radius of curvature being at least 8 millimeters; and
an electrical lead adapted for implantation via the catheter, the lead having a distal tip electrode implantable into a wall of the heart to a depth of at least 2 millimeters, whereby the electrical lead may be implanted through the His bundle and secured into the adjacent ventricular myocardium.
13. The catheter and lead system of
14. The catheter and lead system of
15. The catheter and lead system of
16. The catheter and lead system of
17. A catheter for implanting an electrical lead within a right atrium of a heart in close proximity to a His bundle, the catheter comprising:
a proximal portion; and
a generally hook-shaped distal portion extending distally from the proximal portion, terminating in a distal tip, and being generally planar, the distal portion including first and second segments curved in the same direction, the second segment being more sharply curved than the first segment and shorter than the first segment, the second segment being distal of the first segment and including a generally linear tip segment terminating in the distal tip, whereby, when the catheter is implanted, the curvature of the second segment orients the distal tip in a direction generally perpendicular to the His bundle and the curvature of the first segment pushes the second segment towards the His bundle.
18. The catheter of
19. The catheter of
20. The catheter of
The present invention is related to the delivery of medical electrical leads and more particularly to catheter delivery of such leads to a site in a right atrium of a heart in close proximity to the His bundle.
Various types of medical electrical leads have been developed for endocardial introduction into different chambers of a patient's heart. These flexible leads, various constructions of which are well known in the art, may be delivered using accessory tools, for example a stylet passing through a lumen of a body of the lead, or a catheter having a lumen through which the lead is passed.
A lead implanted in the right atrium can provide pacing therapy to preserve both atrial-ventricular synchronization and the normal ventricular activation and contraction patterns. However, pacing from a right atrial appendage, the typical pacing location in the right atrium, is ineffective if conduction between the right atrium and ventricles is blocked, for example at the AV node of the right atrium. Localized ischemia, inflammation, congenital defects, compression of the AV node, or ablation to prevent conduction as a treatment of atrial fibrillation can be the source of such a block. Ventricular pacing at an apex of the right ventricle is typically employed to bypass such a block, but recent studies have put forth the proposition that problems may arise from pacing at the right ventricular apex because an electrical impulse traveling from the apex moves contrary to the heart's natural conduction pathways. In light of these studies, methods for physiological pacing are currently under investigation; physiological pacing may be defined as stimulation of an intrinsic conduction system of a heart in order to preserve a natural conduction pattern of the heart.
A site of interest for physiological pacing is the His bundle, which is accessible from the right atrium. Existing catheters are not well suited for delivery of an electrical lead to the bundle of His, requiring protracted procedures to reach the desired location. The length of the procedure results in prolonged periods of time in an operating suit causing increased expense and difficulty for the patient as well as greater radiation exposure to the patient. In addition, existing catheters, to the extent they are able to deliver a lead to the His bundle, are generally parallel to the heart surface when they reach the location, making it more difficult to deliver and attach a lead to the underlying cardiac tissue. Thus, there is a need for a tool to facilitate delivery of a medical electrical lead to a site in the right atrium that is in close proximity to the His bundle, for either temporary or permanent pacing stimulation of the His bundle.
Certain embodiments of the invention include a catheter for delivering and implanting an electrical lead to a right atrium of a heart in close proximity to a His bundle. The catheter includes proximal and distal portions. The distal portion may be hook-shaped, generally planar, and may terminate in a distal tip. The distal portion may also have first and second segments, where the second segment is distal of the first. The second segment curves through an arc of about 100 to 160 degrees to orient the distal tip generally perpendicular to a His bundle when the catheter is implanted. The first segment includes a curvature that springs and orients the second portion towards the His bundle when the catheter is implanted.
Certain embodiments of the invention may include a catheter and lead system for implantation in close proximity to a His bundle. The catheter has a proximal portion and a hook-shaped distal portion that terminates in a distal tip. The distal portion extends over 138 millimeters and through an arc of at least 180 degrees and includes first and second segments. Further, the first and second segments include respective first and second radii of curvature, where the first radius of curvature is greater than the second radius of curvature, which is at least 8 millimeters. The second segment is located distal of the first segment and curves in substantially the same direction as the first segment. The system also includes an electrical lead adapted for implantation via the catheter. The lead has a distal tip electrode that may be implantable to a depth of at least 2 millimeters through the His bundle and secured into the adjacent ventricular myocardium.
The following drawings are illustrative of particular embodiments of the present invention and therefore do not limit the scope of the invention. The drawings are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the present invention will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements.
The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the following description provides practical illustrations for implementing exemplary embodiments of the present invention.
When a portion of the heart's intrinsic conduction system becomes damaged, efficient pumping is compromised. A patient, whose SA node 1 has become damaged, may have a pacemaker system implanted wherein lead electrodes are placed in an atrial appendage 15. The lead electrodes stimulate RA 10 downstream of damaged SA node 1 and the stimulating pulse travels on to AV node 2, His bundle 3, and Purkinje fibers 5 to restore physiological contraction of the heart. However, if a patient has a damaged AV node 2, pacing in atrial appendage 15 will not be effective, since the pacing site is upstream of damaged AV node 2. Such a patient may have a pacemaker system implanted wherein lead electrodes are placed in an RV apex 16. RV apex 16 has been an accepted site for pacing since it is a relatively easy to engage lead electrodes at this site, and pacing from this site has been demonstrated safe and effective. Due to questions raised by recent studies looking into long-term effects of pacing from RV apex 16, as previously described, there is a great deal of interest in physiological pacing.
Certain shapes of curves that are pre-formed in catheter distal portion 20, cooperate with surrounding venous anatomy, for example wall 212 of SVC 12, to assist the operator or physician in positioning catheter distal portion 20 and in delivering lead 29, to a site in close proximity to His bundle 3. Alternate embodiments of catheter distal portion 20, including such pre-formed curves, are presented in
With respect to the total curvature of curves 31 and 32, in certain embodiments, curves 31, 32 together extend through an arc of about 180 degrees to about 250 degrees. In certain other embodiments, curves 31 and 32 together extend through an arc of about 200 degrees to about 240 degrees.
With respect to the total curvature of curves 41 and 42, in certain embodiments, curves 41, 42 together extend through an arc of about 180 degrees to about 340 degrees. In certain other embodiments, curves 41 and 42 together extend through an arc of about 250 degrees to about 310 degrees.
The flexible nature of the catheter allows it to advance through the circulatory system and into the heart, while its pre-shaped curved nature provides for proper lead placement. Because the catheter is flexible, it conforms to the shape of the arterial structures as it passes through them and toward the heart. Upon advancing into the right atrium, the catheter rests against the wall 212 of the SVC 12 as described above. Once entering the atrium, a distal portion of the catheter referred to hereinafter as the orienting portion (e.g., at least L32, L25 in
The second curve, 32, 42, is placed in the vicinity of the bundle of His 3 by the shape of the first curve 31, 41. The second curve 32, 42, turns the distal tip 25 of the catheter into a proper orientation relative to the interior surface of the wall of the heart at the location at which the lead will be placed. Thus, as shown in
In certain embodiments, the distal tip 25 of the catheter may contain an electrode that senses when the tip 25 is in contact with the heart wall at bundle of His 3, indicating that the catheter is in a proper location for placement of the lead. This is possible because the bundle of His 3 has an electrical potential waveform, distinct from the surrounding tissue, which is a signature waveform known as the His potential. This signature waveform, which has a frequency of approximately 200 Hz, can be sensed by an electrode in the catheter tip, such as, for example, is used in a mapping catheter.
In certain embodiments, a programmer, such as a modified pacing system analyzer, could be incorporated into the catheter system. However, because such programmers are typically optimized for sensing at a rate of approximately 30 Hz, with slow trace speeds for R-wave and P-wave sensing, the programmer trace speed would have to be modified to adjust for the higher frequency content of the bundle of His 3 potentials.
Once the distal tip of the catheter is in the proper location, the lead 29 is advanced through the catheter and is physically and electrically connected to the heart. This connection may be obtained using a helical coil, as one example, to anchor the lead into the cardiac tissue. The alignment of the catheter tip with the interior surface of the heart, being generally perpendicular to approximately 45 degrees askew, facilitates this connection. Preferably, the connection directly couples the lead 29 to the bundle of His 3. It is also preferable for the connection to also connect the lead 29 with the ventricular myocardium, such as by passing through the bundle of His 3 and into the adjacent ventricular cardiac muscle. A helical coil between approximately 1.5 mm and 3.5 mm in length may be used. However, a relatively longer helical coil of approximately 3.5 mm in length may be preferable, as the increased length may allow for better penetration through the bundle of His 3 and into the myocardium. In some embodiments, the helical coil or other connector may release a bioactive agent, for example, by the elution of a steroid from the coil. The drug released could perform a variety of functions, such as decreasing inflammation. An anti-inflammatory effect could be provided, for example, by a steroid eluting from the coil.
A lead connection that penetrates through the bundle of His and into the myocardium provides several advantages. It provides electrical stimulation of the myocardium around the bundle of His 3, allowing for pacing of the heart through an alternate pathway. Under normal conditions, after placing the lead 29, an electrical stimulus to the bundle of His 3 passes through the left and right bundle branches, down the Perkinje fibers and to the ventricals of the heart. This conduction occurs much more quickly than conduction through myocardium, thus it is the dominant pathway and provides the stimulus for the ventricals to contract. However, this conductive pathway could fail in the future, such as due to damage to a component of the pathway caused by ischemia. Should this occur, the stimulus to the myocardium, provided by the lead and no longer dominated by the normal conductive pathways from the bundle of His, would spread through the cardiac muscles and causes ventricular contraction. Thus the lead would continue to pace the heart using an alternative pathway. In addition to conductive advantages, such placement into the myocardium also provides more secure anchoring for the lead. In addition, if the lead is also used for sensing as well as stimulation, placement into the myocardium provides for better sensing of heart activity than placement into the His bundle 3 alone.
It should be noted that the delivery catheters described herein are constructed according to methods well known to those skilled in the art from well known biocompatible materials, and include basic catheter features, for example, a lumen and one or more radiopaque markers. An overall length of the delivery catheters may be between 30 and 60 centimeters, and an outer diameter of the catheters may be between 6 Fr and 14 Fr (1 Fr=0.013 inch).
In the foregoing detailed description, the invention has been described with reference to specific embodiments. However, it may be appreciated that various modifications and changes can be made without departing from the scope of the invention as set forth in the appended claims.